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The rope ladder of a boat hangs over the side of the boat and just touches the water. The ladder rungs are 8 inches apart. How many rungs will be under the water when the tide rises 3.5 feet? • 1 rung • 2 rungs • 5 rungs • 0 rungs [Default] [MC Any] [MC All]
How much heat would need to be added to a 2.5 kg sample of water in order to increase the temperature from 35oC to 95oC? (Remember Q = mcΔT)cwater = 4190 J/kgoC • 366.6 kJ • 628.5 kJ • 995.1 kJ • 1361.8 kj [Default] [MC Any] [MC All]
Because the rubber ball’s temperature increased faster than the banana dipped in LN2, that means which had a higher specific heat. • The rubber ball • The banana • Both have the same • Neither are capable for getting heat [Default] [MC Any] [MC All]
“Thermodynamics” • Is derived from Greek meaning “movement of heat.”
The First Law of Thermodynamics • Official Definition:When heat flows in or out of a system, the energy it gains or loses is equal to the amount of heat transferred. • Or… Heat = Energy ! • Is analogous to the Law of Conservation of Energy • We are now dealing with Internal Energy
Temperature: • What is it? • How “Hot” or “Cold” a substance is. • Temperature represents the average translational kinetic energy of the individual particles in a system. • The Temperature Scales • Fahrenheit – water freezes at 32oF and boils at 212oF • Celsius – Water freezes at 0oC and boils at 100oC • Kelvin – is based off of Absolute Zero • Absolute Zero • So cold that all particles stop moving! • Total energy of the particles is 0.
Temperature: • Temperature Conversions • Celsius to Fahrenheit • Fahrenheit to Celsius • Celsius to Kelvin • Examples
A piece of metal is heated to 475 oF, what is this temperature in Celsius? • 887 oC • 246 oC • 519 oC • -27 oC [Default] [MC Any] [MC All]
The melting point of copper is 1073 oC. What is this temperature in Kelvin? • 800 K • 1899 K • 578 K • 1346 K [Default] [MC Any] [MC All]
Specific Heat Capacity • What is it? • The resistance to change in temperature of a substance. • The Equation: • Q = mcΔT • Examples:
How much heat energy is required in order to raise the temperature of a 0.5 kg iron nail from a temperature of 25oC to 80oC? • 5750 J • 18400 J • 12650 J • 24150 J [Default] [MC Any] [MC All]
A 75 kg piece of a concrete sidewalk on a sunny day will gain about 650,000 Joules of heat energy from the sun. By how much will its temperature increase on that day? • 25133333 K • 3.0 K • 16810 K • .33 K [Default] [MC Any] [MC All]
An iron pot containing 5 kg of water at an initial temperature of 23oC is placed on a stove. If the stove applies 560,000 Joules of heat energy, what is the final temperature of the water? • 49.7 oC • 26.7 oC • 3.7 oC • 76.5 oC [Default] [MC Any] [MC All]
A cup of water (c=4190) and a piece of metal (c=350) are both left to sit out on a sunny day. By the end of the day, which will have a greater change in temperature? • water • metal • They will have same temperature • I don’t know [Default] [MC Any] [MC All]
The Second Law of Thermodynamics • Official Definition:Heat, of itself, never flows from a colder object to a warmer object. • Energy always flows from Hot to Cold • This law is also called the Law of Entropy
What is Entropy? • The amount of disorder in a system • The universe is always moving towards more entropy • Examples: • Ice melting • Liquid water evaporating • It takes Work (energy) to decrease Entropy
Types of Heat Transfer • Conduction • Heat transfer between materials that are in direct contact with each other. • Convection • Transfer in a fluid by movement of the substance itself. • Radiation • Energy transmitted by electromagnetic waves.
Phase Changes • The States of Matter:
Phase Changes Boiling • Types of Phase Changes: • Melting • Evaporation • Condensation • Boiling • Sublimation Melting Evaporation Condensation Sublimation
Phase Changes • How do you change the melting point or boiling point of a substance? • Add a solute • Change the pressure
Phase Changes • Energy During Phase Changes • What happens to the temperature of water as heat is added? • It Increases. • What happens to the temperature during a phase change? • It remains constant.
Phase Changes • Latent Heat • Latent Heat of Fusion • The amount of energy required to change a unit mass of any substance from a solid to a liquid (and vice versa). • Abbreviated Lf (or Hf) • Latent Heat of Vaporization • The amount of energy required to change a unit mass from liquid to gas (and vice versa). • Abbreviated Lv (or Hv) Lv Lf
Phase Changes • Latent Heat • Equation:Q = mLWhere:Q = heat added during phase changem = mass of sampleL = Latent Heat (of fusion or vaporization) • Examples:
How much heat is required to boil 3.5 kg of water? (Lv = 2.26x106J/kg) • 7910 J • .0001264 J • .0000001264 J • 7910000J [Default] [MC Any] [MC All]
An experiment is performed and it is found that it takes 13.0 x 106 Joules of energy to melt 4.8 kg of iron. What is the Latent Heat of fusion for Iron? • 2.7 x 106 J/kg • 2.7 x 103 J/kg • 6.2 x 107 J/kg • 6.2 x 104 J/kg [Default] [MC Any] [MC All]